This invention concerns brakes and more particularly axially engaged radial face friction brakes.
Such brakes are sometimes designed to be spring engaged, and to be disengaged by an electromagnetic coil energized to attract an axially movable armature which acts to nullify the spring engagement force and release the brake.
The coil must, therefore, be sized to produce a sufficient electromagnetic attractive force on the armature to overcome the operator springs. The springs in turn control the torque capacity of the brake.
The size of the coil is the major factor in the overall size of the brake unit, and also in the cost of manufacture.
One application for such brakes which is receiving increasing attention is in electric motors for power saws in which an automatic brake application to brake the saw blade is highly desirable. The friction type engagement allows stopping without excessive shock loadings, and the controls are easily incorporated in the motor circuit to yield a fail safe engagement.
For radial arm saws, the axial dimension is critical to enable maximum tilt of the blade, and hence it is highly desirable to minimize the coil and coil housing size.
It is, therefore, an object of the present invention to provide such a spring-applied, electromagnetically released brake in which the size of the electromagnetic coil is significantly reduced over conventional designs.
It is another object of the present invention to provide such a brake in an electric motor for fail safe braking applications, such as power saws.